The present invention relates to the separation and the chemical treatment of impurities in a fluid and more particularly relates to the separation and chemical treatment of such impurities in an aqueous environment in order to convert the impurities to a less hazardous or non-hazardous condition.
As more fully disclosed in applicants' above-identified co-pending application, a centrifuge (or some other mechanism for achieving high rotational speeds) provides a system that will permit production of high pressure and high temperatures in a fluid in continuous flow from a low temperature/low pressure liquid. For simplicity, the invention will be disclosed in this application with respect to a liquid aqueous suspension and/or solution. However, it will be understood that the present invention is also applicable to other fluids.
An aqueous liquid achieves a supercritical temperature-pressure state which gives it enhanced ability to promote certain chemical and/or physical changes in the liquid. The critical temperature of water is 705.47.degree. F. (374.15.degree. C.) and its critical pressure is 3208.2 psi. The temperature is called "critical" because above the critical temperature of a substance no amount of pressure will produce its liquid phase. Some solutes in water may increase or decrease that critical temperature.
As described in applicants' said co-pending application, a rotating device, such as a centrifuge or pump, utilizes centrifugal force to provide pressure or vacuum to create and maintain an environment which will initiate and sustain a supercritical condition for a material which occupies the environment. A fluid is in a supercritical condition when the temperature and pressure of a liquid and gas in equilibrium are at, or exceed, a critical temperature (Tc) and a critical pressure (Pc) such that the densities of the liquid and gas become identical. The distinction between the two phases disappears and the resulting substance is described simply as a "supercritical fluid".
At or above supercritical conditions, a mixture of hazardous waste, water, and oxidants can often be chemically altered to produce a mixture which is less hazardous or non-hazardous than the original mixture. As will be described hereinafter in greater detail, a centrifuge device is used as a reactor in a supercritical water oxidation (SCWO) process for the destruction of toxic waste. The centrifuge described herein is used primarily to create a high-pressure environment rather than to separate mixture constituents by density as in conventional centrifuges. The configuration of the centrifuge of the present invention is different from that of conventional centrifuges and employs a novel construction for material containment.
The density of a material in a conventional centrifuge contributes to the creation of pressure and if all other parameters are the same, a denser material will cause a higher pressure at a particular reference point in the centrifuge than a less-dense material will cause at the same reference point. It is a known phenomenon that as the temperature of pressurized water increases, the density of the water decreases. Hence, if a desired pressure is required at a particular reference point, a centrifuge with hot water will have to operate at a greater angular velocity than a similar centrifuge with cold water. In other words, a centrifuge with hot water will have to operate at a greater angular velocity and/or have a greater diameter to produce the same pressure as a similar centrifuge with cold water. Since the SCWO process requires a high temperature, the conventional centrifuges in existence today are unable to easily produce the high pressure for SCWO because of the decrease in density due to the increasing temperature.
When used for the destruction of hazardous waste by a SCWO process, the centrifuges of the present invention will permit the SCWO process to operate more efficiently than existing SCWO processes. The pressure generating ability of the centrifuges of the present invention is not appreciably reduced by a decreasing density due to increasing temperature. The centrifuges of the present invention as disclosed herein will focus on the destruction of hazardous waste by a supercritical water oxidation (SCWO) process although the centrifuges may also be used to other aspects of supercritical fluid technology (SFT).